1. Field of the Invention
The present invention relates generally to wireless communications involving mobile stations, and more particularly to methods and apparatus for facilitating the determination of Global Positioning System (GPS) location information of a mobile station without disrupting voice communications of a voice call.
2. Description of the Related Art
Present-day wireless communication devices, such as cellular telephones or mobile stations, are capable of making and receiving voice calls and/or sending and receiving data through wireless communication networks. Fairly recent developments have given such mobile stations the ability to communicate Global Positioning System (GPS) location information which is indicative of the exact location of the mobile station. To reduce cost and complexity at the mobile station, this may be done using the same RF transceiver utilized for typical voice and data communications (or by sharing at least a portion thereof) without the need for a completely separate GPS transceiver (i.e. separate hardware).
Among the adopted position location technologies for Enhanced 911 (E911), Assisted GPS (A-GPS) is one of the solutions. For current Code Division Multiple Access (CDMA) systems, such GPS techniques are described in standard specification documents such as TIA/EIA/IS-801-1 of November 2000. During a voice call involving the mobile station, real-time GPS location information may be obtained and sent to a receiving entity. To obtain real-time GPS location information, the mobile station receives the signals from a GPS system as well as communicates with a location server in the wireless communication network. The location server may include a Position Determination Entity (PDE) which has a GPS receiver for wirelessly receiving information from the GPS system. The mobile station obtains GPS acquisition assistance data and uses it to perform what is referred to as a “GPS fix” during a voice call. During the GPS fix, the mobile station tunes to a GPS frequency different from the traffic channel of the voice call in order to obtain GPS pseudorange data from the GPS system. The mobile station obtains the GPS pseudorange data by measuring GPS signal delays at the mobile. After the GPS fix, the mobile station retunes back to the traffic channel of the voice call. Sometime during the voice call, the mobile station sends the GPS pseudorange data to the location server which calculates the location of the mobile station based on it. The location server/PDE may send the location of the mobile station to the receiving entity (e.g. 911 emergency center or PSAP) or, if received by the mobile station, the mobile station may send the location of the mobile station to the receiving entity.
Note that the mobile station may have to tune away from the voice call anywhere between about 300 milliseconds to 2 seconds, for example. As apparent voice communications of the voice call are undesirably disrupted with use of the conventional procedure. Also, the conventional procedure undesirably increases the chances of the voice call being dropped. The processes also cause power control variations that can reduce system capacity. In the case where the voice call is very important, such as the 911 emergency call, these issues are of great concern.
Accordingly, there is a resulting need for methods and apparatus for facilitating the determination of GPS location information for a mobile station without disrupting voice communications of a voice call so as to overcome the deficiencies of the prior art.